1. Field of the Invention
The invention relates to the communication between a sender (transmitter) and a receiver over a capacitive coupling (sometimes also referred to as capacitive resistive coupling, “intrabody” coupling or PAN-coupling) in which small electrical currents which are used for the transmission of information between the transmitter and the receiver are produced in the human body, and/or in which the transmitter and the receiver interact with one another over very short distances via electric fields.
2. Description of Related Art
This method of coupling is disclosed in the U.S. Pat. Nos. 4,591,854, 5,914,701 and 5,796,827. Implementations thereof are described in the international patent application PCT/CH 2006/000518 as well as in further published specifications of various bearers.
A particular advantage of the capacitive coupling through the human body or, as the case may be, over short distances is the selectivity of the data transmission. Depending on the configuration, one can determine with a high degree of certainty that the signal received by the receiver can only have been transmitted by the person who is situated in direct proximity to or in physical contact with a receiver electrode that is designated for it.
A disadvantage is, among other things, that as a result of the poor signal to noise ratio (literally: signal-interference ratio), only a small amount of data can be transmitted. A good signal to noise ratio is only possible with a large amplitude of the transmission signal. However, a large amplitude (i.e. high voltage) would not be tolerated by the user. In the international patent publication WO 2007/112609 approaches are described with which these problems can be addressed. Despite these the bandwidth of the signal transmission remains limited.
Many possible applications exist for capacitive resistive data transmission, however known realizations are tailored to particular applications. For a new application, a newly adapted hardware, which is adapted to the specific requirements corresponding to the particular signal to be transmitted and to the physical factors, must be developed. This situation is unsatisfactory.
With this background in mind, it is an object of the present invention to provide solutions for capacitive resistive data transmission which ameliorate the above-mentioned disadvantages at least partly and which mean a further step toward the commercial application of the technology and its acceptance by consumers. The solutions mentioned should, in particular, be utilizable for access control.